docs: def get_mean_and_stddevs(self, sites, rup, dists, imt, stddev_types):
          """
          See :meth:`superclass method
          <.base.GroundShakingIntensityModel.get_mean_and_stddevs>`
          for spec of input and result values.
          """
          mean = self._get_mean(sites, rup, dists, imt, stddev_types)
          stddevs = [np.ones(len(dists.rrup))*get_sigma(imt)]
          return mean, stddevs